2 Weird Issues
 

First, i just changed my thermostat a few days ago, my blower motor is working (wirings a bit weird) but my heat just stopped working.. all that comes out is cold air even when on hot.. my temp only goes to just right before half..

Second, when i changed my thermostat and drove the car out of my garage and let it run a few seconds , my fuel gage started to work again (was stuck at full before ) then dropped to half after . But after about 15 minutes it went back. Im not sure whats wrong .

Btw its a 95 si

first, did you bleed the cooling system after changing the stat? if not thats why your heat doesnt work; you have air pockets in your cooling system.

second, i'd take a guess that your floater on your sending unit isnt functioning properly, or your sending unit itself is malfunctioning and not sending the correct signal for the level of fuel actually in your tank to your fuel gauge. just a guess though, would need proper diagnosing to find the actual proeblem